The present invention is directed to a motor-adjustable head support for a dental treatment chair. As used herein, the term "dental treatment chair" refers to a chair with a reclining capability and an adjustable head support.
Various designs have been developed in an effort to adapt a motion sequence of an adjustable head support of a dental treatment chair to a natural tilting movement of the head of a patient in various treatment positions, predominantly during treatment of a patient's upper or lower jaw while the patient is in a seated or reclined position.
U.S. Pat. No. 4,515,406 discloses a design wherein a carrier plate of a head support, which is also frequently referred to in technical jargon as a "head support sword," is a circularly curved, narrow plate having a center of a circle that lies roughly in a cervical vertebra joint of a patient sitting in a dental treatment chair. The curved plate is guided in a carriage, which is displaceable by a hydraulic drive cylinder along a back rest, and the plate can be moved into and out of the carriage by another hydraulic cylinder drive. First, guidance of the carrier plate along a circular arc and longitudinal guidance of the carriage are relatively complicated; second, a relatively thick design of the back rest is required in order to accommodate these elements, particularly an arcuate plate, inside the back rest in a retracted condition. A preferred embodiment would consist of a thinner back rest in this region in order to be able to position the head of the patient as low as possible in a fully reclined position, but still allow adequate freedom for an attendant's knees. This embodiment, however, would lead to a restriction of the kinematics and, thus, to a restriction of positioning possibilities.
German OS No. 25 41 506 discloses a design of an adaptor element for a head support which adapter has a curved path that, as viewed from the side of the head support, includes oppositely curved sections in a wave-like fashion. The curved patch has a guide arranged at the back rest, whereby the adaptor element has its end facing away from the head support and is connected to a traction or thrust mechanism arranged at the back rest in order to effect an adjustment of the head support. The guide of the curve path is formed by a horizontal rod arranged transversely relative to a longitudinal direction of the back rest with the curve path of the adaptor element resting against the horizontal rod. The horizontal rod is mounted for rotation. The adaptor element has its end facing away from the head support and is pivotably and longitudinally displaceably mounted in a carriage in the back rest with this carriage being adjusted by a another traction or thrust mechanism.
In this design, freedom of leg movement of an attendant is also restricted given a reclined treatment position.